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Feature Article

Obesity – a growing issue for male fertility

Madhuni Herath, Ie-Wen Sim
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Lifestyle and environmental factors

A range of potentially remediable lifestyle factors can affect fertility and should be addressed in all men with subfertility. Some of these factors, such as a sedentary lifestyle, are associated with obesity. 

Sedentary lifestyle. Prolonged sitting, in combination with increased lower abdominal and scrotal fat deposition, might adversely affect sperm production by increasing testicular temperature.

Tobacco. Tobacco use has a modest dose-dependent effect on sperm quality, with lower sperm concentration and poorer sperm motility and morphology seen in smokers.12,13 Furthermore, smoking may decrease the success rate of assisted reproductive technologies, including in vitro fertilisation and intracytoplasmic sperm injection. Sperm isolated from smokers have poorer function and higher DNA fragmentation, suggesting a direct detrimental effect of tobacco on sperm DNA. These outcomes may be reversible within a year of tobacco cessation. 

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Alcohol. Heavy alcohol use may be associated with hypogonadism, poorer sperm quality and sexual dysfunction.

Cannabis. It has been suggested that cannabis may activate cannabinoid receptors located on sperm and the paraventricular nucleus of the hypothalamus. These receptors are believed to be responsible for regulating sperm motility, and sexual and erectile function, respectively. Although cannabis use has been linked with abnormal sperm motility and impaired fertility in male mice,14 human studies are limited. In vitro studies demonstrate a dose-dependent negative effect on sperm motility and function, whereas the impact on sexual function is less conclusive, with some studies reporting enhanced sexual pleasure with cannabis use, but others report impaired erectile function.15

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Management of men who are overweight with subfertility

Patient assessment

Assessment of overweight men with subfertility should include a basic fertility assessment to ensure that other causes of male subfertility are not overlooked.16 The potential contribution of female factors must also be considered. A male fertility assessment tool developed by Healthy Male is available for free download at: www.healthymale.org.au/health-professionals/clinical-resources/patient- assessment-tools. Points to cover in a fertility assessment of overweight men are summarised in the Table

In addition to the basic fertility assessment, evaluation of overweight men should focus on identifying obesity-associated comorbidities and lifestyle factors that may play a significant role in the aetiology of subfertility as well as confer significant cardiovascular risk. Cardiovascular assessment should include inquiring about erectile dysfunction, measuring blood pressure and screening for diabetes and dyslipidaemia. The importance of ED as an independent risk factor for metabolic syndrome and cardiovascular disease is increasingly being recognised, with ED representing a surrogate biomarker for endothelial dysfunction and atherosclerosis. OSA and depression should also be considered in all men who are overweight.

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The initial assessment of a couple with subfertility by a GP can expedite their evaluation and ensure they are referred to an appropriate specialist, such as an endocrinologist and/or a gynaecologist specialising in assisted reproductive technology.

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Dr Herath is the Andrology Fellow at Monash Health, Melbourne, which is supported by Healthy Male (formerly Andrology Australia). Dr Sim is a Consultant Andrologist at Monash Health and Monash IVF; Expert Advisor to Healthy Male; and Consultant Endocrinologist at Monash Health, Eastern Health and Western Health, Melbourne, Vic.